Location and General Description
This ecoregion lies at the delta of the Indus River, which originates in the Tibetan Plateau and flows through the northwestern part of India and into the arid Thar Desert in Pakistan before finally emptying into the Arabian Sea. There are high salinity levels in the sloughs because of the high evaporation rates and the salts that are washed down by the river, which flows through a highly saline area. Climatic conditions are extreme. Ambient temperatures range from near-freezing temperatures in the winter to higher than 50(C during the summer. All rainfall is associated with the July to September southwest monsoon, which brings a mere 100-500 mm of precipitation.
Mangroves in general are not diverse compared with most other terrestrial ecosystems, and undisturbed mangrove forests have a dense canopy with little stratification and an undergrowth made up of seedlings and saplings from the canopy trees. The Indus River mangroves are even less diverse, being composed of nearly monospecific stands of Avicennia marina, a species that is highly resistant to high salinity levels and capable of surviving the region's extreme conditions (Spalding et al. 1997). Other species that are sometimes associated with the Avicennia include Rhizophora apiculata and Acanthus ilicifolius, with occasional smaller patches of Rhizophora mucronata and Ceriops tagal scattered throughout. The former usually is closer to creeks.
This mangrove ecoregion provides important habitat for fish and invertebrates and serves as critically important spawning grounds and nurseries for fishes and aquatic crustaceans.
There are 123 bird species known from this ecoregion, although none are considered endemic to the ecoregion.
Although this area has been heavily degraded and more than 85 percent of the habitat has been lost, several patches of intact habitat still exist. There are three protected areas that cover about 820 km2, or 16 percent of the ecoregion (table 1), but even these protected areas are degraded.
Table 1. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
Protected Area Area (km2) IUCN Category
Marho Kotri 810 IV
Cut Munarki Chach 3 UA
Mirpur Sakro 10 IV
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.
Types and Severity of Threats
Threats to this mangrove ecoregion stem from several sources. Mangroves are cut for fuelwood, the major source of firewood for the more than 10,000 people who live in the area, and for fodder to feed the domestic livestock, which include camels (Spalding et al. 1997).
Other threats stem from industrial pollution from the city of Karachi, oil spills and discharges from the ships that anchor in the city's harbor, and increased salinity levels caused by flow diversions in the Indus River. Seasonal fishers live in the mangrove forests and cut and clear the forests while setting up camps.
Justification of Ecoregion Delineation
We used MacKinnon's (1997) digital map of original vegetation and Spalding et al. (1997) to identify the extent of the mangroves represented in this ecoregion. This ecoregion lies within Udvardy's Thar Desert biogeographic province.
References for this ecoregion are currently consolidated in one document for the entire Indo-Pacific realm.
Indo-Pacific Reference List
Prepared by: Eric D. Wikramanayake